Needle Guidance in Ultrasound Guided Nerve Blocks: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Needle Guidance in Ultrasound Guided Nerve Blocks (NCT02080481), a randomized na study. The primary outcome is Time Spent in Performing Ultrasound Guided Femoral Nerve Blocks With InfinitiPlusTM Needle Guidance System.

2. Clinical Question

The comparison concerns a procedural device and a specific ultrasound-guided nerve block, not surgery or pain outcomes more broadly. The primary endpoint is time spent performing the block, with time measured from the beginning of the procedure after prepping and draping until catheter insertion was successful or the end of the day of surgery. The registry reports this measure as a median and inter-quartile range for each group, and also reports a regression analysis comparing geometric means.

Random assignment makes the groups suitable for a comparative interpretation, subject to the limitations of the registry record and the trial’s execution. The study was not masked. The record does not report the allocation-concealment process or whether clinicians assessing procedural outcomes were independent of the intervention. Consequently, the results describe the observed comparison under this study’s conditions; they do not by themselves establish how the devices would compare in other settings or with other clinicians.

3. Trial Design

The registry describes a randomized, parallel-group trial with no masking. The two groups received ultrasound guidance with either the InfinitiPlus needle guidance system or a conventional block needle. The condition listed is elective knee surgery, and the intervention descriptions specify femoral nerve block procedures. The registry lists enrollment of 135 and reports outcome data for 67 participants in each group. The record does not explain the difference between the listed enrollment and the group counts reported for outcomes, so those figures should be read as recorded rather than reconciled.

The trial status is completed. The registry lists a start date of 2014-03 and primary completion of 2015-12. The phase is listed as NA, and the study type is categorized as other. The sponsor is The Cleveland Clinic. The registry record does not report the trial’s location or the number of clinical sites, so neither should be inferred from the sponsor name.

Randomization supports a comparison between the assigned approaches, but the registry does not report the sequence-generation method, allocation concealment, deviations from assigned treatment, or the analysis population. Masking is explicitly listed as none. The record also does not describe who recorded the procedure times or assessed block failure and needle visibility. These omissions matter because treatment assignment and outcome assessment could be apparent during a procedural study.

The brief summary describes additional aims involving procedure cost and success rate. Cost results are not reported in the registry record. The posted outcomes include block failure, more than one block attempt, and percentage of time with perfect needle visibility, alongside the primary time endpoint. The registry lists four outcome measures overall and reports three secondary outcomes. A full protocol, statistical analysis plan, sample-size justification, and details of interim analyses are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Time Spent in Performing Ultrasound Guided Femoral Nerve Blocks With InfinitiPlusTM Needle Guidance System, measured over time elapsed from beginning the block procedure (after prepping and draping) until the catheter was successfully inserted or the end of the day of surgery..

The primary endpoint is time spent performing an ultrasound-guided femoral nerve block with catheter placement. The registry defines the measurement window as starting after prepping and draping, at the beginning of the block procedure, and ending when the catheter was successfully inserted or at the end of the day of surgery. The endpoint is recorded in seconds. Its stated purpose is to compare the time required for the procedure with InfinitiPlus needle guidance against the time with a conventional block needle.

Procedure time is a continuous measure: a recorded duration can take many values rather than falling into a simple event/no-event category. The registry summarizes each group with a median and inter-quartile range. The median describes the middle of the observed distribution, while the inter-quartile range describes the span from the lower to the upper quartile. These summaries are useful when a typical duration and the spread of observed durations are of interest, without requiring the data to be described only by a mean and standard deviation.

The primary analysis is reported as a ratio of geometric means from linear regression. A ratio compares the groups on a multiplicative scale, rather than expressing a difference in seconds. The registry does not explain the regression model’s covariates, transformations, or other specification details. The endpoint is a measure of procedural duration; it does not directly measure block quality, patient experience, or safety. Those are separate questions, and only some are represented among the posted secondary outcomes.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary ratio mean?

The primary analysis reports a ratio of geometric means. A geometric mean is a way to summarize measurements on a multiplicative scale, and a ratio expresses one group’s estimate relative to the other group’s estimate. A ratio of 1 represents no difference on that scale; values on either side indicate the direction of the comparison once the reference group is known. The reported estimate is 0.68, with a 95% confidence interval from 0.61 to 0.76. In this trial’s reported comparison, the estimate indicates a lower time for InfinitiPlus relative to the conventional needle. The registry does not give enough model detail to independently assess the regression specification or any covariate adjustment.

Why report medians and inter-quartile ranges?

A median identifies the middle observation in an ordered set of measurements. The inter-quartile range gives the interval containing the middle half of the observations. These statistics describe a typical value and the spread around it without assuming that the distribution is symmetric. Procedure times can be unevenly distributed, so a median can be a useful descriptive summary. The reported medians and inter-quartile ranges are group summaries, not a direct estimate of the adjusted regression contrast. A difference between the group medians should not be substituted for the reported ratio of geometric means.

How should the confidence intervals be read?

A confidence interval expresses uncertainty in an estimated quantity under the statistical model and sampling assumptions. A narrower interval indicates greater precision than a wider interval on the same scale; an interval spanning the no-effect value indicates that the estimate is compatible with no difference at the corresponding confidence level. The primary interval lies below the ratio value of 1. The registry reports 95% confidence for this analysis. For secondary outcomes, the sponsor’s analyses are reported with 98.3% confidence intervals. Confidence intervals do not account for every possible source of uncertainty, including measurement problems, incomplete reporting, model misspecification, or the limits of generalizing beyond the study.

What do the unadjusted recalculations add?

For the binary secondary outcomes, a risk difference compares the observed proportions with the event in the two groups. A value of zero represents equal observed proportions. The recalculated comparisons use the posted group counts and are unadjusted; they are not the sponsor’s regression analyses. The confidence intervals describe uncertainty in those simple comparisons. For the continuous needle-visibility outcome, the recalculation uses a difference in group means. A mean difference of zero represents no difference in the group averages. These recalculations are useful as a transparent comparison based on the posted summaries, but they do not replace the sponsor’s own analyses.

The sponsor’s regression results can differ from unadjusted recalculations because regression may use a different model or account for variables that a simple comparison does not. The registry does not report enough detail about the model specifications, covariates, coding, or analysis populations to fully explain each contrast. Where the reported odds ratio’s direction depends on how the outcome and reference group were coded, the estimate should not be interpreted without those details.

Why does multiplicity matter?

When a trial evaluates several outcomes, the chance of finding at least one apparently noteworthy result by chance can rise if each is tested independently without an adjustment or prespecified hierarchy. This is the general statistical reason that secondary outcomes often need more cautious interpretation than a single primary outcome. The registry lists four outcome measures and three secondary outcomes. It does not report whether the outcomes were prespecified in a protocol, how they were ordered, or whether any correction for multiple comparisons was planned. The posted secondary p-values therefore should not be read as if multiplicity had been addressed.

What are the planning illustrations?

Planning estimates based on an observed effect are illustrations of the sample size that could be needed under stated assumptions; they are not evidence that the completed trial had a particular probability of detecting an effect. The registry’s planning assumptions specify a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects defined as fractions of the observed effect. For non-time-to-event outcomes, the estimates are participants per arm. These illustrations use observed effects and should not be mistaken for the trial’s original design justification. The registry does not report the original sample-size justification, and the illustrations do not provide observed power.

10. Analyses Reported by the Sponsor

The sponsor’s primary analysis is the reported regression comparison of geometric means: ratio 0.68, 95% confidence interval 0.61 to 0.76, and p < 0.001. The group medians and inter-quartile ranges are descriptive summaries, not a recalculation of that regression model. The registry does not provide the model specification or adjustment details, so the relation between the regression estimate and the raw summaries cannot be fully reconstructed from the record.

For the secondary outcomes, the sponsor reports logistic regression for block failure and more than one block attempt, and linear regression for perfect needle visibility. The simple recalculations use the posted group summaries and are unadjusted. Their estimates, confidence intervals, and p-values can differ from the sponsor’s because the methods and potentially the outcome coding or adjustment differ. The registry does not report the necessary details to resolve those differences fully. In particular, the reference-group coding for odds ratios is not described.

The record does not flag a discrepancy between sponsor analyses and recalculations. The sponsor’s estimates should therefore be read as the registry’s reported model results, while the unadjusted recalculations are supplementary views of the posted summary data. Neither set of secondary analyses should be treated as definitive without the prespecified analysis plan and model details, which are not reported in the registry record.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures, including the primary procedure-time endpoint and three posted secondary outcomes. It does not report whether the secondary outcomes were formally prioritized, whether a testing hierarchy was specified, or whether p-values or confidence intervals were adjusted for multiple comparisons. When several outcomes are examined, unadjusted statistical tests can produce apparently notable results by chance even if no true differences exist. This general concern makes the secondary results less conclusive than a prespecified primary result considered on its own. It does not invalidate the reported estimates, but it limits how strongly they can be interpreted.

Missing-data handling is not reported in the registry record. The record does not explain whether all randomized participants contributed to each outcome, how unavailable or incomplete measurements were treated, or whether any imputation or sensitivity analysis was used. The outcome counts list 67 participants in each group, but those counts alone do not establish the analysis population or show whether every randomized participant had complete data. The relationship between the listed enrollment and the group counts is not explained.

Analysis populations are also not reported. The registry does not say whether the analyses followed assigned groups regardless of treatment received, included only participants who received the assigned device, or used another approach. It does not describe protocol deviations, exclusions, or the handling of crossover. Such information is important for interpreting a randomized comparison and assessing whether the analysis preserves the benefits of random assignment.

The registry reports no masking, but does not describe blinding of outcome assessors or who recorded procedure times. It also does not report the allocation-concealment method, sample-size justification, interim analyses, or a complete statistical analysis plan. These are not grounds to assume that a particular practice was or was not used; they are details that are not reported in the registry record.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The posted safety figures list zero serious adverse events and zero other adverse events in each group, with 67 participants at risk in each group for both categories. The registry does not list any serious-event terms. These figures mean that no serious or other adverse events are recorded in the posted results for the groups and categories reported. They do not establish that no events occurred outside the registry’s recorded categories, that every event was captured, or that risk is absent.

Deaths are not reported in the registry record. The adverse-event information is therefore incomplete for a full safety assessment, and it should be read as a limited account of recorded events rather than a comprehensive safety evaluation. The registry’s safety figures also do not provide enough context to assess event definitions, the observation period, or how events were collected and adjudicated. They should not be used to draw conclusions beyond the reported counts.

13. What the Result Does, and Does Not, Mean

The primary result describes a difference in procedure time between ultrasound-guided femoral nerve blocks performed with InfinitiPlus needle guidance and those performed with a conventional block needle in this randomized trial. The observed group medians were 118 seconds and 177 seconds, respectively, and the reported regression ratio was 0.68 with a 95% confidence interval from 0.61 to 0.76. The p-value was p < 0.001. These statistics indicate that the trial’s primary analysis found a difference in the measured procedure time, with the reported estimate favoring a shorter time in the InfinitiPlus group.

This result does not establish that every procedure will be shorter, quantify the experience of an individual clinician, or show that all aspects of the block procedure differ. The secondary outcomes are less conclusive, and cost results are not reported in the registry record. The time endpoint also does not directly measure patient experience or broader clinical outcomes. The posted adverse-event figures are limited and do not establish the absence of risk.

The finding applies to the population, procedure, and comparator described in the registry record. The trial involved patients having elective knee surgery and a femoral nerve block with a catheter. The record does not report enough information about study sites, clinician characteristics, outcome assessment, analysis populations, or model specification to determine how well the results extend to other settings or practice patterns.

Statistical significance is not the same as proof that an effect is important in every practical context. The registry does not specify a threshold for a clinically meaningful change in procedure time, and no such threshold should be inferred. The estimates and intervals describe statistical evidence and uncertainty, not a guarantee of a particular outcome. The results also do not answer the broader questions in the study summary unless results for those questions are posted.

14. Why This Trial Matters Statistically

This trial illustrates why the choice of summary and analysis matters in procedural research. Procedure time is reported with medians and inter-quartile ranges, while the primary comparison is a ratio of geometric means from regression. Those summaries answer related but different statistical questions. Reading them together requires distinguishing a description of observed group distributions from a model-based comparison.

It also shows how a clear primary comparison can coexist with less decisive secondary results. Procedure time, block failure, repeated attempts, and needle visibility measure different aspects of a procedure. A result for one does not automatically carry over to the others. In the absence of a reported multiplicity plan, several secondary comparisons need cautious interpretation, even when an unadjusted estimate appears suggestive.

The record further demonstrates the value of reporting model details and analysis decisions. The sponsor’s regression results and simple unadjusted recalculations are not identical kinds of evidence. Without information on coding, covariates, missing observations, and analysis populations, readers cannot fully reproduce or reconcile every contrast. Such details help clarify what an estimate means and how robustly it can be interpreted.

Finally, planning illustrations based on observed effects should be separated from a trial’s original design rationale and from observed power. The registry does not report the original sample-size justification. Keeping planning estimates distinct from evidence about the completed study prevents an effect observed in one trial from being mistaken for a design assumption or a guarantee of future precision.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Several trial-specific limitations follow from what the registry does and does not report. The study was not masked. The record does not say whether outcome assessors were masked or independent, or how procedure time was recorded. Because the outcomes concern an observable procedure, knowledge of the assigned device could affect behavior or measurement; the extent of any such influence cannot be determined from the registry record.

The primary analysis is described as linear regression with a ratio of geometric means, but model details are not reported. The registry does not specify covariates, transformations, assumptions, or checks of model fit. The record also does not explain the coding and reference group for the secondary odds ratios. These omissions limit independent assessment of the sponsor’s estimates and their relationship to the unadjusted recalculations.

The record does not report missing-data procedures, analysis populations, allocation concealment, or a complete statistical analysis plan. Nor does it report the original sample-size justification or how the primary endpoint was selected relative to the additional aims. The outcome reporting does not include results for cost, although cost is described as a study question. The reason that result is absent is not reported in the registry record.

Finally, the registry does not report the number of sites or enough participant and clinician detail to assess generalizability. The enrollment and group outcome counts are both listed, but their relationship is not explained. The listed safety results are limited to the reported adverse-event categories, and deaths are not reported. These gaps do not negate the primary result, but they restrict assessment of how complete, reproducible, and broadly applicable the findings are.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Needle Guidance in Ultrasound Guided Nerve Blocks — NCT02080481.
• Registry record last updated 2017-05-15; status last verified 2017-04.
• Results first posted 2017-05-15.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry describes a completed, randomized, parallel-group study with no masking, comparing ultrasound-guided femoral nerve blocks using the InfinitiPlus needle guidance system with blocks using a conventional needle. The listed condition is elective knee surgery, enrollment is 135, and the sponsor is The Cleveland Clinic. The registry lists a start date of 2014-03 and primary completion of 2015-12.

The primary endpoint is procedure time. The reported group medians were 118 seconds for InfinitiPlus and 177 seconds for the conventional needle. The sponsor’s regression analysis reported a ratio of geometric means of 0.68, with a 95% confidence interval from 0.61 to 0.76 and p < 0.001. Three secondary outcomes are posted, but their results are less conclusive overall. The registry does not report cost results, full analysis details, missing-data handling, or a multiplicity plan. The adverse-event figures list no serious or other events in either group; deaths are not reported in the registry record.